Single nucleotide polymorphism in hMLH1 promoter and risk of tobacco-related oral carcinoma in high-risk Asian Indians

Abstract

hMLH1 is a member of mismatch repair genes (MMR) that plays a crucial role in correcting replication errors, cell cycle arrest, apoptosis and oxidative stress. We explored the risk associated with hMLH1 -93 A>G (rs 1800734) single nucleotide polymorphism (SNP) with the oral squamous cell carcinoma (OSCC) in Asian Indians. We genotyped 242 patients with tobacco-related OSCC and 205 healthy controls by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique. The frequency of AA genotype was found to be significantly (Pc<0.0006) lower in patients as compared to the controls (21.49% vs. 47.8%) while GG genotype showed significantly higher (Pc<0.0006) prevalence in patients as compared to the healthy controls (41.32% vs. 13.66%). In logistic regression analysis AG (adjusted OR=1.95, 95% CI=0.72-5.26) and GG genotype (adjusted OR=4.5, 95% CI=1.54-13.16, P=0.006) appeared susceptible when compared with the wild-type AA genotype. The allelic distribution showed that variant G allele is significantly higher (Pc<0.0004) in patients and associated with increased risk (adjusted OR=2.36, 95% CI=1.33-4.19, P=0.003) as compared to the wild-type A allele. Altogether, our results suggest that the hMLH1 -93 A>G polymorphism is associated with the higher risk of tobacco-related OSCC in Asian Indians and could be useful in screening population at a higher risk.

Keywords: Asian Indians; BPDE; DNA repair capacity; DRC; GT-IIB; GT-motif 2B; HNPCC; MMR; MSH2; MutS homolog 2; NF-IL6; OSCC; Oral cancer; PCR-RFLP; SNP; UICC; Union for International Cancer Control; benzo(a)pyrene diol epoxide; hMLH1; hereditary non-polyposis colorectal cancer syndrome; human MutL homolog 1; interleukin 6-regulatory nuclear factor; mismatch repair; oral squamous cell carcinoma; polymerase chain reaction-restriction fragment length polymorphism; single nucleotide polymorphism.